Bill Stepien, Christie’s former campaign manager, is citing Constitutional protections against self-incrimination and unreasonable search and seizures in refusing to turn over records to the New Jersey Legislative Select Committee. He’s not the only former aide to refuse to comply with the investigation; the lawyer for Bridget Anne Kelly, Christie’s former deputy chief of staff who was fired after the scandal came to light, said a subpoena issued to her was “constitutionally defective.”

Stepien’s attorney sent a letter to the attorney hired by the committee saying, “his principled objections to the subpoena raise significant legal issues that are no less valid because they here arise in the context of a politically-charged investigation.” The letter said the attorney could think of “no lawful way” that the committee could obtain the documents it seeks in a subpoena.

New Jersey State Sen. Loretta Weinberg, the co-chair of the committee, said that the next step would be to take the matter to court. Other key figures in the scandal have also cited Constitutional issues in refusing to comply with the committee’s subpoenas.

The committee investigating the September closure of lanes on the George Washington Bridge has issued nearly 40 subpoenas to determine who authorized the closures and whether they were politically motivated. Christie’s administration came under fire earlier this year after it emerged that aides had deliberately snarled traffic on the bridge out of apparent retribution at the mayor of Fort Lee, N.J, who had refused to endorse the governor in his re-election bid. Christie has repeatedly said he knew nothing about the scheme.